The long-term goal of this project is to understand the function of the serglycin proteoglycan. This proteoglycan is contained in the secretory granules of all but erythroid hematopoietic cells, endothelial cells, embryonic stem cells, and murine uterine decidua during pregnancy. The putative roles of serglycin include complexing with and packaging secretory proteins into granules, regulating their release either constitutively or during cell activation, and modulating their activity and delivery to target cells. The serglycin proteoglycan itself may have specific functions in terms of interaction with cells or extracellular matrices. The secretory proteins which interact with serglycin include chemokines, cytokines, extracellular matrix proteins, and a number of proteases. Thus serglycin may modulate important physiologic activities mediated by these secreted proteins such as blood coagulation, immune function, inflammation, early embryonic development, and embryonic implantation. Many studies which have been performed in vitro suggest the importance of the serglycin proteoglycan and its glycosaminoglycan chains in these processes. However, the true function of serglycin in the course of packaging and ultimately directing these proteins to their cellular targets can only be determined in vivo. Therefore we are proposing to generate mice with global, conditional, or cell-specific deletion of the serglycin gene. First, using a targeting vector which we have prepared and electroporated into embryonic cells, we will obtain embryonic stem cell clones which will be used to generate heterozygous and then homozygous serglycin null mice. Second, we will generate a targeting vector containing loxP sites flanking critical regions of the serglycin gene. Embryonic stem cells targeted with this vector can be used to generate mice which can in the future be crossbred with mice containing either inducible or cell-specific ere recombinase in order to obtain inducible or cell-specific knockouts of the serglycin gene. These animals can in turn be bred with mouse models of thrombotic or atherosclerotic disease. The experiments will ultimately delineate the role of serglycin in modulating a variety of critical physiologic functions in normal and disease states. [unreadable] [unreadable]